首页 | 本学科首页   官方微博 | 高级检索  
     


Conformationally Rigid Chiral Bicyclic Skeleton‐Tethered Bipyridine N,N′‐Dioxide as Organocatalyst: Asymmetric Ring Opening of meso‐Epoxides
Authors:Elumalai Gnanamani  Nagamalla Someshwar  Jayakumar Sanjeevi  Chinnasamy Ramaraj Ramanathan
Abstract:The conformationally rigid chiral bicyclic skeleton tethered bipyridine N,N′‐dioxide (−)‐ 9 has been designed, synthesized and examined as an organocatalyst in the enantioselective ring opening of meso‐epoxides using tetrachlorosilane (SiCl4). The catalyst (−)‐ 9 is found to exhibit good enantioselectivity for substituted cis‐stilbene epoxides; whereas, the saturated cyclic meso‐epoxides display a moderate enantioselectivity. At −30 °C in chloroform, the catalyst (−)‐ 9 with 0.5 mol % loading generated the chlorohydrins in up to 97 % yield with up to 93 % ee. The possible creation of transient axial chiral environment around hypervalent silicon species due to the presence of conformationally rigid chiral bicyclic skeleton tethered bipyridine N,N′‐dioxide may be responsible for such enantioselectivity observed in the desymmetrization of meso‐epoxides.
image

Keywords:asymmetric synthesis  catalyst design  chiral bipyridine N,N′  ‐dioxide  desymmetrization of meso‐epoxides  organocatalysis
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号